Why did Kirk Gibson let Ian Kennedy throw 50 pitches in an inning?

Ian Kennedy had a terrible night in St. Louis on Thursday. The 28-year-old Diamondbacks righty was tagged for 13 hits and 10 runs in four innings during a 12-8 loss, but what was alarming was the way manager Kirk Gibson left him to twist in the wind during an endless fourth inning. At the very least, Gibson's inaction widened a deficit that Arizona ultimately couldn't overcome; at most, it may have exposed a pitcher who two years ago was one of the league's best to an unnecessary risk.

Kennedy faced 11 batters in that 25-minute frame, allowing eight runs via six hits and two walks. A misplay that he himself made loomed large; he could have escaped the inning having allowed just one run if his throw to second base on Yadier Molina's potential double play grounder weren't well offline. After that, he unraveled, yielding a five-pitch walk to Matt Holliday (who had hit a two-run homer off him in the second inning), a two-run single to Allen Craig, a three-run homer to Matt Adams, an eight-pitch walk to David Freese and then a two-run homer to Daniel Descalso (who had led off the inning with a double) before striking out Jon Jay for the third out.

By the time the dust settled, Kennedy had thrown an alarming total of 50 pitches in the inning — the second-highest single-inning total in the majors this year, and the highest by a Diamondback since Doug Davis threw 44 in an inning on June 10, 2009 — long before Gibson was manager. Asked about his starter after the game, Gibson told MLB.com:

"We need around 100 [pitches] from him, no matter what…

"I didn't have a choice… It happened quick. You wouldn't expect it to get away from him -- but it did. You don't ever want to leave anybody in that long."

It wasn't exactly clear why Gibson was so insistent on Kennedy throwing 100 pitches or why the manager was so slow with his hook. Arizona won a 14-inning game on Tuesday, but among the relievers Gibson used in that game, only Josh Collmenter had thrown more than 22 pitches, and in Wednesday's win, the team needed just 21 pitches from three relievers over 2 1/3 innings.

Within the context of the game, what was also odd was that Gibson let Kennedy bat for himself shortly afterward, down 10-2 in the bottom of the fourth with one out and nobody on base. He struck out, then was pulled before the top of the fifth, having thrown a total of 99 pitches. Reliever Matt Reynolds instantly widened the gap to 12-2 by allowing solo homers to pitcher Shelby Miller and Matt Carpenter. The Diamondbacks eventually scored three runs in the seventh inning and three more in the ninth, forcing Cardinals manager Mike Matheny to call upon closer Edward Mujica to finish the game. Had Gibson acted earlier and not left Kennedy to grit it out — or seized the opportunity to try to start something in the home half of the fourth — the contest might have been more competitive.

In the larger scheme, it's Kennedy's 50-pitch inning that stands out. With the increased emphasis on pitch counts since the turn of the millennium, teams and managers have used mileposts such as 100, 120 or 130 total pitches as rough guidelines, with much debate surrounding whether those rather arbitrary numbers actually protect pitchers' arms. What has gotten less attention is that teams have grown conscious of single-inning pitch counts as well, because running up such high totals without a break is believed to place an undue amount of stress on a pitcher's arm. Some organizations mandate the automatic removal of their minor league pitchers above 35 or 40 pitches.

As far back as 2004, then-Giants head trainer Stan Conte (now vice president of medical services for the Dodgers) said in a Baseball Prospectus chat, "We track all innings over 25 pitches as a stressful inning. Some pitchers may only throw 100 pitches but throw them in four innings. So on the surface it looks like their count was not high but they put a far amount of stress on their arms if they throw 35 pitches in one inning."

Given that emphasis, high pitch count innings are relatively rare. According to data from the PITCHf/x gurus at BrooksBaseball.net, since the beginning of the 2009 season, pitchers have thrown at least 40 pitches in an inning 371 times, which averages out to 85 a year (prorating this year), or roughly three per team per year. Only 65 pitchers have gone above 45 pitches in an inning in that span, an average of 15 per year, or one per team every two years. Kennedy's outing tied for the seventh-highest total in the majors since 2009 (keep in mind that the f/x data may not exactly match official pitch count totals):

Such high pitch counts in an inning aren't a death sentence, but that's not a particularly encouraging leaderboard on which to be included, as many of those pitchers have since had injury problems or faded away from the major league scene due to ineffectiveness (then again, the same could be said for just about any pitcher-based leaderboard given enough time). While McAllister, Kendrick and Maholm are currently upstanding members of their respective rotations, Sanchez, the previous high-scorer this season, was released by the Pirates shortly afterward due to continued ineffectiveness. Bedard is notoriously injury prone and has become increasingly ineffective, while Danks and Pelfrey are working their way back from recent surgeries in less than impressive fashion, with current ERAs of 5.63 and 6.40, respectively. Snell and Coleman were already on the fringes of the majors and have since faded into obscurity. Poor Davidson only got that one inning at the major league level.

None of those pitchers besides Kennedy has ever been considered a staff ace. In 2011, Kennedy went 21-4 with a 2.88 ERA and finished fourth in the NL Cy Young voting. While one can understand any manager relying on his best pitcher to work out of a jam, Kennedy doesn't appear to be that guy anymore. Last year, his ERA rose to 4.02, and after Thursday's outing, he's at 5.72 this year. His home run rate has nearly doubled since 2011, from 0.8 per nine to 1.5, and his strikeout and walk ratios have moved in the wrong directions such that his 3.6 ratio in 2011 has declined to 2.4 — respectable, but a steep decline nonetheless.

Kennedy doesn't appear to have any significant health concerns to explain his decline. He recently missed a turn due to a laceration on his finger, but had thrown seven innings and 89 pitches in his previous outing on June 1. His fastball velocity has remained relatively stable -- around 90 mph -- since coming to the Diamondbacks for the 2010 season, and after flagging midway through the fourth last night, it recovered, though by that point he found himself well in the proverbial weeds.

It's entirely possible that Kennedy's epic inning won't leave any lasting mark. But particularly so long as he continues to struggle, it's worth keeping an eye on his performance — and the way Gibson handles his pitchers.

Special thanks to Harry Pavlidis of BrooksBaseball.net for research help with this article